Havanatur (Calle 23, esq. M, Vedado, tel. 07/830-3107 or 201-9800, daily 8 a.m.–8 p.m.) offers a city tour, including walking tour, plus excursions to key sights in the suburbs and, of course, farther afield.
Agencia de Viajes San Cristóbal (Oficios #110, e/ Lamparilla y Amargura, tel. 07/861-9171, www.viajessancristobal.cu [1], daily 8:30 a.m.–5 p.m.) offers a wide range of excursions throughout the city—from a walking tour of Habana Vieja (daily 10 a.m.) to an “Eclecticismo y Modernismo” tour of modern Havana for architecture buffs.
You can book through hotel tour bureaus.
Agencia de Viajes San Cristóbal (Oficios #110, e/ Lamparilla y Amargura, tel. 07/861-9171, www.viajessancristobal.cu [1], daily 8:30 a.m.–5 p.m.) can arrange guides.
Jineteros (street hustlers) will offer to be your guide. Perhaps they can show you the offbeat scene that most tourists miss, but they’re usually useless as sightseeing guides and most will pull a scam.
Links:
[1] http://www.viajessancristobal.cu